Electric Motor Thermal Management - Department of · PDF file• Improve cooling methods to...

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NREL is a national laboratory of the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, operated by the Alliance for Sustainable Energy, LLC. Electric Motor Thermal Management Kevin Bennion National Renewable Energy Laboratory May 15, 2013 Project ID: APE030 This presentation does not contain any proprietary, confidential, or otherwise restricted information.

Transcript of Electric Motor Thermal Management - Department of · PDF file• Improve cooling methods to...

Page 1: Electric Motor Thermal Management - Department of · PDF file• Improve cooling methods to reduce heat flow through critical or variable interfaces. Passive Thermal Design • Thermal

NREL is a national laboratory of the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, operated by the Alliance for Sustainable Energy, LLC.

Electric Motor Thermal Management

Kevin Bennion National Renewable Energy Laboratory May 15, 2013

Project ID: APE030

This presentation does not contain any proprietary, confidential, or otherwise restricted information.

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Overview

Project Start Date: FY 2010 Project End Date: FY 2013 Percent Complete: 80%

• Cost • Weight • Performance & Life

Total Project Funding: DOE Share:$1,900K (FY10-FY13)

Funding Received in FY12: $550K Funding for FY13: $500K

Timeline

Budget

Barriers and Targets

• Interactions / Collaborations – University of Wisconsin (UW) – Madison

(Thomas M. Jahns) – Oak Ridge National Laboratory (ORNL) – Motor Industry Representatives

• Project Lead – National Renewable Energy Laboratory

Partners

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Relevance/Objectives

The transition to more electrically dominant propulsion systems leads to higher-power duty cycles for electric drive systems.

Continuous Operating Limit

Torq

ue

Speed

Thermally Limited Area of Operation

Transient Operating Limit

Thermal management is needed to reduce size and improve performance of electric motors. • Meet/improve power capability within

cost/efficiency constraints • Reduce rare earth material costs (dysprosium)

Targets Efficiency (%)

Cost ($/kW)

Weight (kW/kg)

Volume (kW/L)

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Relevance/Objectives

The transition to more electrically dominant propulsion systems leads to higher-power duty cycles for electric drive systems.

Continuous Operating Limit

Torq

ue

Speed

Thermally Limited Area of Operation

Transient Operating Limit

Objectives • Quantify opportunities for improving cooling technologies for electric motors • Link thermal improvements to their impact on Advanced Power Electronics and

Electric Motors (APEEM) targets • Increase information related to motor thermal management in open literature

Addresses Targets • Translates cooling performance improvements into impacts on program targets • Prioritizes motor thermal management efforts based on areas of most impact

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Milestones

Date Description January 2012 Go/No-Go

• Completed selected motor lamination material thermal property tests • Decided to not expand material tests at this time

July 2012 Go/No-Go • Thermal sensitivity analysis showed significant impact common to multiple

motor configurations leading to future project proposals for specific convective cooling enhancements and passive stack thermal improvements

September 2012 Milestone report • Lamination material thermal properties and motor thermal sensitivity

analysis

December 2012 Milestone (internal) • Completed transmission oil test bench for oil cooling experiments

September 2013 Milestone report • Final project summary report on lamination material thermal properties,

motor thermal sensitivity analysis, and oil heat transfer experimental data • Summarize collaborative motor cooling efforts with Oak Ridge National

Laboratory (ORNL)

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Approach/Strategy

FY13 Focus

Credit: Kevin Bennion, NREL

Interior Permanent Magnet (IPM) Model Cross Section Transmission Oil Heat Transfer Experimental Setup

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Approach/Strategy Cooling Technology Selection • Characterize heat transfer

coefficients of oil impingement cooling

• Investigate wire insulation reliability o Oil cooling impingement o High-potential breakdown

voltage tests

Credit: Kevin Bennion, NREL

Oil Impingement Test Chamber IPM Motor Model

IPM Motor Cooling Schematic Motor Axis

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Approach/Strategy

IPM Motor Model Cross Section

Passive Thermal Design • Thermal interfaces between contacting

components provide significant resistance to heat flow.

• Interfaces are often difficult to characterize experimentally.

• Manufacturing variability increases the uncertainty of the interface thermal resistance.

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Approach/Strategy

• Develop baseline performance data from analytical and experimental methods.

• Investigate concepts to enhance or improve effective component thermal properties.

• Improve cooling methods to reduce heat flow through critical or variable interfaces.

Passive Thermal Design • Thermal interfaces between contacting

components provide significant resistance to heat flow.

• Interfaces are often difficult to characterize experimentally.

• Manufacturing variability increases the uncertainty of the interface thermal resistance.

IPM Motor Model Cross Section

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Approach/Strategy 2012

Oct

Nov

Dec

2013

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Complete transmission oil loop construction and preliminary testing

Heat transfer measurements of transmission oil jets/sprays and winding insulation reliability

Go/ No-Go

In Progress

Legend

Complete

Obtain Baseline Data for Potential Future

Focus Areas

Collaboration with ORNL • Thermal analysis and design support

of motor developments conducted at ORNL

Milestone

Final Project Report

Continue baseline measurements of passive thermal design elements • Slot Windings • Laminations • Contact Interfaces

ORNL Induction Motor

Credit: Sreekant Narumanchi, NREL

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Technical Accomplishments and Progress Completed phase one of partnership with the University of Wisconsin – Madison

• Review of thermal analysis and cooling techniques for traction drive motors • Developed a computationally efficient technique for estimating the loss

components in IPM motors as a function of the motor’s operating point • Developed a 3D finite element analysis (FEA) thermal model for a concentrated

winding stator motor configuration • Developed a thermal equivalent circuit (TEC) model for an IPM concentrated

winding motor

Preliminary thermal FEA showing temperature drop across slot liner for case cooled machine and thermal

gradients in winding Comparison of TEC model with FEA

temperature predictions

Concentrated winding motor

Slot Liner Credit: Thomas M. Jahns, Seth McElhinney (UW–Madison)

Winding

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Technical Accomplishments and Progress Initiated phase two of partnership with the University of Wisconsin – Madison

• Model experimental validation and improvement • Investigating improved heat spreading methods

Litz Type 1 Twisted Wire Bundles

All Images - Credit: Thomas M. Jahns, Seth McElhinney (UW–Madison)

Untwisted Wire Bundles

170°C Maximum Temperature 139°C Maximum Temperature (Same Scale)

Preliminary analysis of twisted wire bundles show a hot spot temperature reduction of 30°C at rated torque and power

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Technical Accomplishments and Progress

Cross Slot Thermal Conductivity

• Improvements to the slot filler material have little impact without improvements to the wire insulation thermal conductivity.

- 20 gauge Slot Winding Thermal Conductivity

0.155 W/m-K 0.11 W/m-K

78% Fill Factor with 20 Gauge Round Wire (Maximum Fill Factor)

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Technical Accomplishments and Progress

Cross Slot Thermal Conductivity

• Improvements to the slot filler material and wire insulation are needed for reduced fill factors.

Slot Winding Thermal Conductivity

0.155 W/m-K 0.11 W/m-K

- 20 gauge 70% Fill Factor with 20 Gauge Round Wire

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Technical Accomplishments and Progress

Cross Slot Thermal Conductivity

• Rectangular wire shows lower thermal conductivity at the same fill factor because of the lower conductivity filler material.

• Benefit of rectangular wire is seen if the thickness of the filler material boundaries are reduced.

20 gauge

Slot Winding Wire Shape

5.5 mm

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Technical Accomplishments and Progress Oil Loop Experimental Setup • Mercon LV Transmission Fluid • Initial heat transfer tests focused on jet

impingement on target surface • Future work

• Alternative heat transfer coefficient measurement techniques

• Expand number of jets, target size, and target surface

• Wire insulation impacts

Test Chamber Credit: Kevin Bennion, NREL

Jet Orifice

Jet Target Surface

Resistive Heater Thermochromic Liquid

Crystal Thermocouple Surface Temperature Estimate

Alternative Convection Coefficient Measurement Methods

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Technical Accomplishments and Progress

Credit: Gilbert Moreno, NREL

Credit: Gilbert Moreno, NREL

Area averaged heat transfer coefficient at 50°C fluid temperature

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Collaboration and Coordination • University

– University of Wisconsin – Madison o Support with electric motor expertise

• Industry

– Motor industry suppliers, end users, and researchers o Input on research and test plans

• Other Government Laboratories

– Oak Ridge National Laboratory o Support from benchmarking activities o Ensure thermal design space is appropriate and modeling assumptions are

consistent with other aspects of APEEM research o Collaboration on motor designs to reduce or eliminate rare-earth materials

– Other Vehicle Technology Office (VTO) areas o Collaborate with VTO cross-cut effort for combined cooling loops

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Future Work

Package Mechanical

Design

Cooling Technology Selection

Thermal Design Targets

Package Mechanical Design • Thermal tests of interfaces and materials

Cooling Technology Selection • Characterization of oil-cooling heat transfer coefficients • Oil cooling reliability tests (winding insulation)

Motor Thermal Design Targets • Collaboration with ORNL • Thermal analysis and design support of motor

developments conducted at ORNL

Credit: Sreekant Narumanchi, NREL

Credit: Gilbert Moreno, NREL

ORNL Induction Motor

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Summary Relevance • Impacts the transition to more electrically dominant propulsion systems with higher continuous power

requirements • Enables improved performance of non-rare earth motors and supports lower cost through reduction

of rare earth materials used to meet temperature requirements (dysprosium)

Approach/Strategy • Engage in collaborations with motor design experts from industry, university, and national labs • Perform in-house thermal characterization of materials, interface thermal properties, and cooling

techniques • Collaborating with ORNL to provide motor thermal analysis support on related motor research at

ORNL

Technical Accomplishments • Completed thermal sensitivity analysis for a range of motor configurations and over a range of

operating conditions in collaboration with the University of Wisconsin – Madison • Evaluated impact of winding material improvements leading to future experimental test plans • Initiated heat transfer characterization tests involving transmission oil

Collaborations • University of Wisconsin – Madison • Oak Ridge National Laboratory • Motor industry representatives: manufacturers, researchers, and end users (light duty and heavy duty)

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For more information, contact:

Principal Investigator Kevin Bennion [email protected] Phone: (303)-275-4447

APEEM Task Leader:

Sreekant Narumanchi [email protected] Phone: (303)-275-4062

Acknowledgments:

Susan Rogers and Steven Boyd, U.S. Department of Energy Andy Wereszczak, John Miller, Tim Burress, Randy Wiles, and Curt Ayers, Oak Ridge National Laboratory Team Members:

Justin Cousineau Douglas DeVoto Mark Mihalic Gilbert Moreno Thomas M. Jahns (UW–Madison) Seth McElhinney (UW–Madison)